The invention relates to an arrangement on multi-colour rotary printing presses for application of liquid to a printing unit cylinder, wherein the liquid is successively transferred from a liquid tank to a fountain roller driven by a separate drive, the fountain roller engaging a transfer roller in turn feeding an applicator roller engaging a plate cylinder driven by the press drive, and wherein means are provided for throwing on and off the applicator and fountain roller.
It is well known that in offset printing the fresh ink on a printed sheet must be prevented from smearing. Diverse methods, such as heaters or powder, are known for this purpose. In all these methods it has been found that the ink gloss is also affected. To retain the original gloss, varnishes are now used and a further system on the printing press is required to apply the varnish. West German patent 2,020,584 describes a device which transfers a suitable varnish to the printing plate by the dampening unit of the offset press and via a rubber blanket to the printing carrier.
But when the dampening unit is used as a varnishing unit it is difficult to use a varnish having an arbitrary viscosity, because the varnish takes a defined path through the dampening unit and the evaporation of the varnish solvent is fixed by the defined path. The same varnishes, however, cannot always be used for the most diverse sheets or impressions encountered in the printing industry. In the known types of dampening units the fountain and metering rollers of a dampening unit are driven by an auxiliary motor, and the successive transfer and applicator rollers are driven by the press drive.